Exogenous nitric oxide-induced germination associated with pinitol content in Hymenaea courbaril low vigour seeds

Nitric oxide (NO), a membrane-permeable free radical, has been reported as a potent signalling molecule in animals and plants. It is commonly accepted that NO induces dormancy release and promotes seed germination. However, few studies were carried out with seeds of tropical arboreal species, which present distinct characteristics compared to temperate model seeds, in order to confirm a broad role of NO in seed germination. To our knowledge, this is the first work to investigate the role of exogenous NO on the germination of seeds accumulating cell wall polysaccharides as the main carbon reserve. The aim of this study was to evaluate the effect of NO donors on germination and primary metabolism of seeds from Hymenaea courbaril L., a leguminous tree species from Neotropical rainforests. Seeds with distinct vigour rates, namely lower vigour seeds (LVS) and higher vigour seeds (HVS), were imbibed in distilled water (control) and NO donor solutions, and selected parameters such as germination rate and normal seedlings, root growth, and metabolic profile were evaluated. Our results show that NO donors reduced the average time of germination and improved normal seedling development of LVS, without affecting the final germination rate. This treatment also induced changes in the relative proportion of soluble sugars and cyclitols identified by gas chromatography–mass spectrometry analysis. Taken together, our data suggest that exposure to the NO donor partially revert deterioration on naturally ageing seeds, possibly through the modulation of pinitol content, and open new perspectives to enhance the existing knowledge on the role of NO on seed viability.